Titration and AcidBase Neutralization Titration A laboratory method

Titration and Acid-Base Neutralization

Titration: A laboratory method for determining the concentration of an unknown acid or base using a neutralization reaction.

Analyte – the substance that is being tested or analyzed. Ex. The concentration of glucose in blood Titrant- a solution of reagent that reacts with the analyte. The concetration of this reagent is accurately and precisely known.

Titration: A standard solution, (a solution of known concentration), is used.

Equivalence Point The point at which there are stoichiometrically equivalent amounts of acid and base. [H+] = [OH-]

Buret Valve

Titration Acid with Phenolpthalein End-Point

Indicators are chosen, such that they change colors at the range of the p. H of interest. The solution itself at the end-point may be: n Basic, if the reaction involves a strong base and a weak acid. n n Neutral, if the reaction involves a strong acid and a strong base. Acidic, if the reaction involves a strong acid and a weak base.

Requirements The reaction must be stoichiometric The reaction must be rapid The reaction must be quantitative There should be marked change in some property of the solution when the reaction is complete.

Methods of Solving Titration Problems: a) using stoichiometry b) using the titration formula a. Ma. Va=b. Mb. Vb.

Ex. 1 What is the concentration of HCl if 30. 0 m. L of 0. 10 M Na. OH neutralizes 50. 0 m. L HCl? Na. OH + HCl H 2 O + Na. Cl Hint: Use a. Ma. Va=b. Mb. Vb Ma = How many moles of HCl were used? Hint: #moles= Ma. Va , but convert the volume to L( 50 m. L=0. 05 L).

Ex. 2 A 20. 0 m. L solution of Sr(OH)2 is neutralized after 25. 0 m. L of standard 0. 05 M HCl is added. What is the concentration of Sr(OH)2? 2 HCl + Sr(OH)2 2 H 2 O + Sr. Cl 2

Ex. 3 How many m. L of 0. 20 M H 3 PO 4 are needed to neutralize 55. 0 m. L of a 0. 10 M solution of Na. OH?

Ex. 4 What volume of 0. 20 M Ca(OH)2 will neutralize 45. 0 m. L of a 1 M solution of HCl. O 3?

Titrimetric Methods : Direct Titration- the reactants involved in the titration reaction are primarily the titrant and the analyte. a. A + t. T → p. P

Standardization Potassium hydrogen phthalate, KHC 8 H 4 O 4 (MM= 204. 23), is a primary standard acid that reacts with sodium hydroxide on a 1: 1 molar basis. Results showed that 0. 5893 g of primary standard grade potassium hydrogen phthalate required 22. 49 ml to reach the phenolpthalein end point. Calculate the molar concentration of the Na. OH solution

2. If 4. 37 ml solution HCl solution were required to titrate a solution containing 221. 4 mg of primary standard sodium carbonate (MM= 105. 99), Calculate the molarity of the solution

Standardization of a Basic Solution A 0. 1105 g sample of primary standard grade Na 2 CO 3 (105. 99) was dissolved in 55 ml of distilled water. The solution required 22. 18 ml of HCl solution to reach the methyl orange end point. a). Calculate the number of mmol of the primary standard grade Na 2 CO 3. b). How many mmoles of HCl reacted with the Na 2 CO 3? c). Calculate the molarity of the HCl

Analysis of Impure sample A 0. 3147 g sample containing Na 2 CO 3 was dissolved in 60 m. L of distilled water and 2 -3 drops of methyl orange were added to the mixture. The solution needed 38. 73 m. L of 0. 1214 M HCl to reach the methyl orange end point

A. Calculate the number of mmol of HCl needed to reach the methyl orange end point. B. How many mmol of Na 2 CO 3 reacted with the HCl? C. Calculate the mass (g) of Na 2 CO 3 present in the sample D. What is the % Na 2 CO 3 present in the sample.